It depends on what your uses are for it. If it is for drills or demonstrations. Depening on you art, you could twist your wrist to add that extra umph.

During sparring I find it better to break tradition and just do standard stright punches like in boxing or MMA with a mid to high guard.

A standard MMA boxing punch is closer to reach your opponents head by .1 or .2 seconds considering trained artists can punch 3 to 4 times in a single second. And to add that to knock someone out: an untrained person only needs 5lbs of force to be knocked out and avg people are capable of generating a lot more than that.

If you use Kyokushin Karateka rules and cant make hand or arm contact with the face and to the body. To generate more force till it hurts is good if you rotate it and adding your own body weight. But lacks defense to protect your head.